A Generic Interface for the Public Bulletin Board Used in UniVote

To provide verifiability, cryptographic voting protocols usually require a public bulletin board for publishing the election data, so that the data can be read and verified by everyone. The basic requirements on such a board are similar for most protocols, for example that nothing can be changed or deleted from the board. Typically, when it comes to implement a voting protocol in a real system, many additional requirements arise and they can differ from protocol to protocol. This paper shows based on the protocol of UniVote what these requirements might be and what other problems may arise from an operational and organisational point of view. Based on the understanding of these problems, we propose a generic interface for the main board functionalities. This interface offers a flexible way of extending the properties of a public bulletin board to comply with all sorts of additional requirements. We give multiple examples of properties that we identified as desirable for the public bulletin board in UniVote.